[Tandum (Robin)]

I finally got some images out of my little starlight express mono camera with a set of trutek filters attached to the tak. I don't understand why there are halos around the big stars in the attached image. I captured, calibrated, stacked and colour converted this image in maxim.

I'm was just looking at image scale tonight and this was shot at 820mm, I'm shooting it again now at 632mm to compare.

I do have a badder IR filter on the nose of the filter wheel but I am yet to do a G2V test on the filters and I'm thinking that's the problem. Any other clues?